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J. Virol., Apr 1996, 2101-2106, Vol 70, No. 4
GC Newbound, JM Andrews, JP O'Rourke, JN Brady and MD Lairmore
Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent of adult
T-cell leukemia/lymphoma and is associated with a variety of
immunoregulatory disorders. HTLV-1 has been shown to bind to and infect a
variety of hematopoietic and nonhematopoietic cells. However, both in vivo
and in vitro, the provirus is mostly detected in and preferentially
transforms CD4+ T cells. The molecular mechanism that determines the CD4+
T-cell tropism of HTLV-1 has not been determined. Using cocultures of
purified CD4+ and CD8+ T cells with an HTLV-1 producing cell line, we
measured viral transcription by using Northern (RNA) blot analysis, protein
production by using a p24 antigen capture assay and flow cytometric
analysis for viral envelope, and proviral integration by using DNA slot
blot analysis. We further measured HTLV-1 long terminal repeat-directed
transcription in purified CD4+ and CD8+ T cells by using transient
transfection assays and in vitro transcription. We demonstrate a higher
rate of viral transcription in primary CD4+ T cells than in CD8+ T cells.
HTLV-1 protein production was 5- to 25-fold greater in CD4+ cocultures and
mRNA levels were 5- fold greater in these cultures than in the CD8+
cocultures. Transient transfection and in vitro transcription indicated a
modest increase in basal transcription in CD4+ T cells, whereas there was a
20-fold increase in reporter gene activity in CD4+ T cells cotransfected
with tax. These data suggest that unique or activated transcription
factors, particularly Tax-responsive factors in CD4+ T cells, recognize
regulatory sequences within the HTLV-1 long terminal repeat, and this
mediates the observed enhanced viral transcription and ultimately the cell
tropism and leukemogenic potential of the virus.
Copyright © 1996, American Society for Microbiology
Human T-cell lymphotropic virus type 1 Tax mediates enhanced transcription in CD4+ T lymphocytes
Center for Retrovirus Research, Ohio State University, Columbus, Ohio 43210, USA.
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